The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In a typical spot welding system, opposing electrodes pass current pass through a pair of metal sheets to be welded together. The electrodes are also employed to hold or clamp the sheets during the welding process. In this arrangements, there are three sources of electrical resistance: i) resistance arising from the resistivity of the material; ii) contact resistance at each electrode-sheet interface; and iii) contact resistance at between the two sheets (known as the faying surface). Additional current paths may form through previously made welds (known as shunt welds).
If the contact resistance at the faying surface is below a desired threshold, the rate of heating required to form a weld may not be high enough because of the high electrical and thermal conductivity of the metal. If, however, the contact resistance at the faying surface is too high, excess current may be diverted to the shunt welds and, further, the weld may exhibit metal rupture.
Accordingly, there is a need for a more efficient spot welding process.